1. Technical Field
The present invention is directed to a lighting fixture unit including semiconductor light-emitting elements. The lighting fixture unit can be used, for example, in a vehicular headlamp. The technology allows formation of a light distribution in upper beam irradiation and an infrared light distribution in lower beam irradiation.
2. Description of Related Art
it is known to use an infrared noctovision camera system to make an obstacle, which is difficult to perceive with visible light, visible during night traveling by using illuminated infrared rays. An infrared floodlight is used as an active-type element of such a system.
When the infrared floodlight is provided as a lighting fixture unit that is separate from a vehicular headlamp, there exist the problems of an increased number of units and an increased unit size. Thus, a configuration using a lighting fixture unit, having a light source that includes a white light source and an infrared light source in a package, is known.
For example, there is a configuration in which separate light-emitting diodes (LEDs) are used for visible light and for infrared light, and a reflector is included. This configuration includes an LED for visible light and an LED for infrared light provided in close proximity to one another. Visible light and infrared light emitted from these elements are reflected in a forward direction by a reflector (for example, refer to JP-A-2004-241138).
Illumination by such a vehicular headlamp includes an upper beam (beam for traveling) irradiation configuration and a lower beam (beam for passing) irradiation configuration. For example, in the following configurations, the lighting fixture units are discriminated based on this feature.
(1) A configuration where a light-emitting element for lower beam irradiation and an infrared light-emitting element are packaged; and
(2) a configuration where a light-emitting element for upper beam irradiation and an infrared light-emitting element are packaged.
In the configuration (1), for example, a white LED for lower beam irradiation is arranged on a board and an infrared LED is arranged in close proximity to the element. In a lighting fixture unit using these elements as a light source, both of the elements are caused to illuminate in lower beam irradiation.
For example, in the configuration (2), a white LED for upper beam irradiation is arranged on a board, and an infrared LED is arranged in close proximity to the white LED. In a lighting fixture unit using these elements as a light source, only the white LED is caused to illuminate in upper beam irradiation, while only the infrared LED is caused to illuminate in lower beam irradiation.
The above configurations (1) and (2) have the following problems related to application of the invention to a vehicular headlamp.
For example, in the configuration (1), two LEDs illuminate at the same time in lower beam irradiation. This requires a large-scale structure or members (such as a heat sink) used for heat radiation of the LEDs.
In the configuration (2), the problem is that the light distribution related to the white LED for upper beam irradiation is the same as that related to the infrared LED for lower beam irradiation. To be more precise, the center of emission of each of these LEDs cannot be specified to the same position. Using one of the centers of emission causes an influence of dislocation on the other. Setting the emission position of each LED by using an intermediate position of the centers of emission causes an influence of dislocation on both LEDs. Forming the same light distribution using individual LED light sources set in separate positions on the same board is difficult or leads to a complicated arrangement in terms of optical design.